Since external apparatuses such as tablet PCs, notebook PCs, cellular phones, televisions; etc, are small in volume and light in weight, they can present good features in carrying and moving. However, these external apparatuses are made into a light, thin and compact configuration. Thus, as compared with desktop computers, their extension is not good. The extension means extended functions, such as printing, scanning, modulating, demodulating, reading data from various mediums, etc. In order to be connected to external devices such as printers, scanners, modulator, demodulator, CD-ROMs, etc, it is necessary to provide interfaces corresponding to these devices respectively on the external apparatuses. But in the external apparatuses required to be miniaturization, it is hardly to insure spaces for these interfaces. Therefore, aiming at such disadvantage, it has developed an electronic apparatus used for extending functions of an external apparatus. The electronic apparatus is, for example, a dock, an external connection device, a cradle, a holding device and a supporting device, etc. When the external apparatus is used indoors, the external apparatus is put onto the electronic apparatus. Thus, a connector of the external apparatus is plugged to a connector of the electronic apparatus so as to achieve an electrical connection to interchange data. It can extend the functions of the external apparatus by connecting the electronic apparatus to various external devices.
However, in prior arts, the electronic apparatus such as a dock is integrated. One type of the dock is only suitable for one type (one thickness) of the external apparatus. It must to use another dock when a user wants to put an external apparatus with different type onto the dock. Thus, it will increase use-cost of the user.